1. Field of the Invention
This invention relates generally to flexible seals, and is concerned in particular with an improvement to seals of the type employed on the tapered sections of roll necks journalled for rotation in rolling mill oil film bearings.
2. Description of the Prior Art
FIG. 1 illustrates a prior art neck seal 10 of the type described in U.S. Pat. No. 4,586,720 (Simmons et al.). The seal has a molded flexible circular seal body 12 internally reinforced by an embedded combination of a coiled spring 14 and a steel cable 16. The seal body has oppositely protruding water-side and oil-side lips 18, 20, a first oil-side flange 22 adjacent to a second oil-side flange 24 commonly referred to as a "flinger", and a third water-side flange 26. The flanges 22, 26 are provided respectively with angularly disposed peripheral lips 28, 30. The lip 28 projects from flange 22 in the direction of the second flinger flange 24, which in turn projects in the same direction at an angle with respect to flange 22 to define a space "S" therebetween open to the surrounding atmosphere.
As shown in FIG. 2, the seal 10 is adapted to be mounted on the tapered section 34 of a rolling mill roll neck 36 which in turn is rotatably supported in an oil film bearing. The bearing includes a sleeve 38 fixed to the roll neck by conventional means (not shown) for rotation therewith. The sleeve 38 has an outer cylindrical bearing surface which is journalled for rotation within an interior bearing surface of a fixed bushing 40. The bushing is carried in a bearing chock 42.
The sleeve rotates with the roll neck while the bearing chock and the bushing remain stationary. Highly viscons oil in flooding quantity is fed continuously between the bearing surfaces of the sleeve 38 and bushing 40. A circular extension 44 of the bearing chock provides a sump 46 in which the oil emerging from between the bearing surfaces is continuously collected. Highly viscons oil may be drawn away from the sump through a suitable piping connection (not shown) to be cooled and filtered before being recycled back to the bearing surfaces.
Where the roll is operating under "wet" conditions, water is constantly flooding over the roll barrel 48 and down over its end face 50. In spite of the centrifugal forces which tend to throw the water off of the roll, some of the water tends to work its way along the roll neck in the direction of the bearing. The objective of the seal assembly generally indicated at 52 and the flexible neck seal 10 which forms a component part thereof is to prevent any of the water from infiltrating into the bearing and contaminating the bearing oil while at the same time preventing loss of oil from the bearing.
In addition to the flexible seal 10, the seal assembly 52 includes a rigid circular seal end plate 54 which is mounted on and fixed relative to the bearing chock 42. The seal end plate has a radially inwardly extending rigid circular flange or "dam" 56 which is perpendicular to the bearing axis. The inner edge of the dam is spaced radially from the flexible seal body. The seal end plate further includes shoulders 58 extending in opposite directions from the base of the dam 56. Each of the shoulders 58 has a cylindrical shoulder surface 60 which is parallel to the bearing axis. The cylindrical shoulder surfaces 60 surround the flexible seal flanges 22, 26, and are arranged to be slidingly contacted by their respective flexible lips 28, 30.
The seal assembly 52 also includes an inner seal ring 62 with resilient buttons 64 engaging the end face 50 of the roll. The inner edge of the inner seal ring contacts the flexible seal body 12 at the juncture of the lip 18 and flange 26.
During a rolling operation, the above-described arrangement will operate in the following manner: the inner seal ring 62, flexible neck seal 10 and sleeve 38 will rotate with the roll neck. The seal end plate 54, chock 42 and bushing 40 will remain stationary. Lubricating oil will constantly flow from between the bearing surfaces of the sleeve 38 and bushing 40. Most of this oil will be turned back by the rotation flinger 24 on the neck seal and will thus be directed to the sump 46. Oil which succeeds in passing by the flinger 24 will be turned back by the rotation oil-side flange 22 and will be prevented from escaping between the flange 22 and the shoulder surface 60 by the flexible lip 28 which sealingly engages the shoulder surface. Likewise, the major portion of the water applied to the roll will be turned back by the rotating inner seal ring 62. Any water which succeeds in passing by the inner seal ring will be turned back by the rotating water-side flange 26 on the neck seal and will be prevented from passing between the flange and its surrounding shoulder surface by the flexible lip 30.
Although the above-described arrangement operates in a generally satisfactory manner, experience has indicated that during removal of the bearing assembly from the roll neck, it happens by design that oil-side flange 22 of the seal is engaged by the dam 56 of the seal end plate 54. This occasionally causes the flange 22 to be bent to an extent sufficient to bring it and its peripheral lip 28 into contact with the second flinger flange 24. The space S is thus substantially reduced in size and closed off from the surrounding atmosphere by the lip 28 in contact with flinger flange 24. This condition is illustrated in FIG. 3A. The space S is further reduced in size and sealing from the surrounding atmosphere increased through the presence of residual amounts of the highly viscous oil used to lubricate the bearing.
Thereafter, as depicted in FIG. 3B, when the bearing is remounted on the roll neck and the seal end plate 54 is again located between and spaced axially from both flanges 22, 26, the flange 22 will seek to resiliently return to its normal position but will be prevented from doing so by the development of subatmospheric air pressure in the closed space S. Thus, the lip 28 will remain out of contact with the adjacent seal end plate shoulder surface 60, resulting in leakage of oil. This development of subatmospheric air pressure will be encouraged by the reduction in size of the air space and improvement in sealing from the surrounding atmosphere through the presence of residual amounts of the highly viscous lubricating oil.